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PEM fuel cell passive water management

a technology fuel cell, applied in the field of proton exchange membrane (pem) fuel cells, can solve the problems of affecting the affecting the overall efficiency of the fuel cell process, so as to reduce parasitic power, improve the pem fuel cell stack, and improve the efficiency.

Inactive Publication Date: 2005-07-12
AUDI AG
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0004]Objects of the invention include a PEM fuel cell stack which does not require a mechanical water pump or a water accumulator; a PEM fuel cell of greater efficiency; a PEM fuel cell which is more suited to use in environments in which the temperature is liable to carry the fuel cell stack below the freezing temperature of water; a PEM fuel cell stack having reduced parasitic power; improved PEM fuel cell stack.
[0005]The invention is predicated partly on the realization that a fuel cell having porous water transport plates will have some frozen water released almost immediately upon startup of the fuel cell, whereby the need for water in an accumulator is avoided, thereby avoiding further the need for a pump.
[0010]An enhancement uses a hydrophobic band or hydrophobic spots in the porous plates to control leakage of gas, to thereby ensure adequate flow to provide wetting of the porous plates.

Problems solved by technology

The accumulator takes up space which is scarce, particularly in electric vehicles powered by a fuel cell.
Furthermore, the parasitic power requirement of the electric pump detracts from the overall efficiency of the fuel cell process.
Additionally, startup in such a system with a frozen pump and conduits can be extremely difficult if not impossible.

Method used

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  • PEM fuel cell passive water management
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Examples

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Embodiment Construction

[0021]In a fuel cell stack illustrated in FIG. 1, all of the fluids have multi-pass flow fields. Specifically, the fuel cell stack 11 has an internal coolant inlet manifold 12, and an internal coolant exit manifold 13. The coolant therein flows through each fuel cell 14 from the inlet manifold 12 to the right, and then flows through the center of the fuel cell toward the left, whereupon it flows rightwardly toward the coolant exit manifold 13, in generally-S-shaped channels, the direction of flow being demarcated by the arrows and dotted lines in FIG. 1. There may be on the order of 18-24 coolant channels in each of the three coolant flow paths demarcated by the dotted lines of FIG. 1.

[0022]The fuel cell has an inlet manifold 16 for fuel reactant gas, which may be hydrogen or a hydrogen-rich stream obtained by reforming a hydrocarbon. Fuel flow fields in each fuel cell comprise fuel flow channels on one surface of a porous anode plate, which extend between the manifolds 16 and 17 an...

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Abstract

Water flow field inlet manifolds (33, 37) are disposed at the fuel cell stack (11) base. Water flow field outlet manifolds (34, 38) are located at the fuel cell stack top. Outlet and inlet manifolds are interconnected (41-43, 47, 49, 50) so gas bubbles leaking through the porous water transport plate cause flow by natural convection, with no mechanical water pump. Variation in water level within a standpipe (58) controls (56, 60, 62, 63) the temperature or flow of coolant. In another embodiment, the water is not circulated, but gas and excess water are vented from the water outlet manifolds. Water channels (70) may be vertical. A hydrophobic region (80) provides gas leakage to ensure bubble pumping of water. An external heat exchanger (77) maximizes water density differential for convective flow.

Description

TECHNICAL FIELD[0001]This invention relates to proton exchange membrane (PEM) fuel cells in which no water pump is provided, water inlet being at the bottom of the fuel cell stack and water outlet being at the top of the fuel cell stack, with or without circulation of the water, and with venting of gas bubbles from reactant leakage through porous water transport plates.BACKGROUND ART[0002]Conventional PEM fuel cells may employ a water management system which includes porous water transport plates which have reactant gas on one side and water on the other side. Such systems generally include a water pump, and an accumulator, together with a gas separator which is required for effective pumping with low cost pumps. The accumulator takes up space which is scarce, particularly in electric vehicles powered by a fuel cell. Furthermore, the parasitic power requirement of the electric pump detracts from the overall efficiency of the fuel cell process.[0003]Furthermore, when a PEM fuel cell ...

Claims

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Application Information

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Patent Type & Authority Patents(United States)
IPC IPC(8): H01M2/36H01M2/12H01M2/00H01M2/08H01M2/14H01M2/02H01M8/02H01M8/04H01M8/10H01M8/00H01M
CPCH01M8/0267H01M8/04029H01M8/04074H01M8/04134H01M8/04253Y02E60/50H01M8/241H01M8/2483H01M8/2457H01M8/0263H01M8/0258
Inventor GRASSO, ALBERT P.SCHEFFLER, GLENN W.VAN DINE, LESLIE L.DUFNER, BRIAN F.BREAULT, RICHARD D.
Owner AUDI AG
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